Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 12: Symposium “Coated HTS Conductors”

TT 12.5: Talk

Tuesday, March 27, 2007, 11:00–11:15, H20

Switching and Quench Propagation in Coated Conductors for Fault Current Limiters — •Helmut Kinder¹, Jörg Handke¹, Werner Prusseit¹, Andrej Kudymow², Christian Schacherer², and Mathias Noe² — ¹THEVA Dünnschichttechnik GmbH, Ismaning — ²ITP, Forschungszentrum Karlsruhe

We address the use of coated conductors for resistive fault current limiters. Fast quench propagation is essential to let the conductor switch on the full length within milliseconds. The ordinary thermal quench propagation mechanism, however, is too slow because of the small heat diffusivity in typical tape substrate materials. Here we present a new mechanism involving a propagating instability of the superconductor made possible by the particular conductor design. The instability is based on current bunching leading to overcritical current densities and does not rely upon thermal conductivity. It leads to a rapid spreading of the resistive state so that the conductor develops its full normal resistance in a millisecond. Thus the conductor protects itself without the need of thick normal conducting stabilizers that would reduce the current limiting efficiency. The mechanism was confirmed by numerical simulations and by experiments on samples of short and medium length. Conductor lengths of 1 m and more switched homogeneously exhibiting voltage drops of up to 2.7 V/cm.